Let's have a photo of the 'spike'. Stress sometimes induces a spike on an orchid. If the plant is sickly, it might be better to abort the spike and let it grow some roots. Sometimes, when oncidiums have bad roots, they grow air-roots and these seem to come from everywhere. Your plant might be growing a root instead of a spike. Give it a few days and you will be able to tell the difference.
Best of luck with it!